In high speed large capacity optical networks that support today's advanced information and communication companies, wavelength multiplexing optical communication technology is used. Reconfigurable optical add drop multiplexers (ROADM) that provide reconfigurable add drop functionality are being introduced into optical nodes that correspond to branching points of an optical network. Wavelength selective switches (also referred to as WSS) that switch any wavelength in any direction are garnering attention in the implementation of ROADM devices. Optical beam deflection elements that select a wavelength and deflect an optical beam to a desired output port are used in wavelength selective optical switches, and that which uses a diffraction phenomenon by liquid crystal on silicon (LCOS) is used in Patent Documents 1 and 2. Further, that which uses mechanical displacement of a mirror array, or MEMS (micro-electro-mechanical system), is used in Patent Documents 3 and 4.